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Preallocate entries slice in DeserializeEntries to reduce allocations #285

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Merged
bdon merged 1 commit into from
Jul 13, 2026
Merged

Preallocate entries slice in DeserializeEntries to reduce allocations #285

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6 changes: 4 additions & 2 deletions pmtiles/directory.go
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Original file line number Diff line number Diff line change
Expand Up @@ -323,8 +323,6 @@ func SerializeEntries(entries []EntryV3, compression Compression) []byte {
}

func DeserializeEntries(data *bytes.Buffer, compression Compression) []EntryV3 {
entries := make([]EntryV3, 0)

var reader io.Reader

if compression == NoCompression {
Expand All @@ -338,6 +336,10 @@ func DeserializeEntries(data *bytes.Buffer, compression Compression) []EntryV3 {

numEntries, _ := binary.ReadUvarint(byteReader)

// Preallocate the entries slice to the known count so the append loops below
// do not repeatedly reallocate and copy the backing array as it grows.
entries := make([]EntryV3, 0, numEntries)

lastID := uint64(0)
for i := uint64(0); i < numEntries; i++ {
tmp, _ := binary.ReadUvarint(byteReader)
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